Choose the right beverage

Sometimes the simplest solution is the best, and that’s true when it comes to choosing a workout beverage.

“If you’re an average person, then water after a workout is just fine,” says Clark. But if your workout is more intense and you spend more than three hours at a time doing it, then Clark recommends chocolate milk. "It’s got sodium and calcium, which we lose when we sweat. It’s also got carbs to refuel and give energy, and the protein also helps to repair any damage.”

If milk or water isn’t your thing, sports drinks, coconut water, or other beverages are fine. Don't worry too much about electrolytes; Clark says food can provide those lost in sweat.

Consume the right amount

Clark says there isn’t a set amount of water that you should consume during exercise, rather, she recommends you “drink to thirst.”

But there are ways to calculate your sweat rate, which involve weighing yourself before and after you run, and doing a few calculations. Clark says that if you lose a quart of sweat in an hour then you should be drinking about eight ounces of water every 15 minutes.

If you want to skip the math and you tend to sweat a lot, 4 to 6 ounces every 15 to 20 minutes during your workout is a good rule of thumb.

Don’t drink too much

It’s actually possible to drink too much fluid, although this is uncommon. More of a risk during marathons and triathlons, athletes who consume a lot of fluid (even sports drinks), but not enough sodium can develop a potentially life-threatening condition called hyponatremia. (A women died of it during the 2002 Boston Marathon.)

Pack in some protein and carbs

While exercising is good for you, it’s common to incur some minor cell or tissue damage after a workout. Proteins can help repair any damage, so Clark recommends rehydrating with a protein-rich drink after an especially intense workout.

But it’s not just about protein, she says. Because you expend substantial amounts of energy when exercising, "you want about three times more carbohydrates than protein," which is why she recommends flavored milk as fluid replacement.

Know the risks of dehydration

Any number of problems can result from not drinking enough water; perhaps one of the most common is fatigue.

If you don’t drink enough water then “your blood gets thicker from lower water content and your heart has to work harder, which means you get tired,” says Clark. “A dehydrated person will get fatigued.”

Drink before and during exercise

Clark recommends drinking fluids before you even begin to exercise, especially if you’re doing something that requires a lot of stamina. "You need to start drinking about one and a one half to two hours before running a marathon," she says.

Also, drinking fluids during a workout isn’t a bad idea either. "We don’t drink enough during exercise and that puts you in a hole when you finish and then you have to rehydrate," says Clark. "It’s better if you don’t put yourself in that hole in the first place."

While it might be cumbersome to carry water with you on a run, it’s worth it, she says.